The present invention relates to a dosage system for a static mixer, in particular a micro-reactor, and a control method thereof.
Static mixers, such as micro reactors, serve for mixing and/or reacting fluids or reactants contained therein. Static mixtures comprise at least one, usually two inlets for the one or more fluids and conventionally said fluids are fed to the mixer by a pump, in particular a piston pump. Such pumps, however, generate pressure fluctuations within the mixer due to their cycle-periodic characteristics. Since in particular in micro-reactors, small-dimensioned static mixers with structured inner cavities and surfaces and with or without temperature control, higher pressures are necessary, enormous pressure pulses occur in such conventional systems. FIG. 3A thereto depicts feed pressure delivered by a conventional piston pump to a microreactor. Such pressure fluctuations, in particular pressure pulses, as occurring in conventional systems including delivery pumps, may adversely affect the chemical reactions within the reactor (selectivity, reaction mechanism, formation of byproducts etc.), in particular if the reaction is micro-mixing controlled or pressure dependent.
In order to apply a desired quantity of fluids, the mass flow rate of each fluid must be measured and controlled with high precision.
A known method for measuring mass flow rates is a so-called coriolis mass flow controller (CMFC). A CMFC comprises a long metal tube vibrating with a certain amplitude. However, these vibrations may degrade the stability of the apparatus and the characteristics inside the microreactor. Furthermore, with known CMFCs the minimum mass flow for accurate measurement must be at least 10 g/min. Additionally, in order to achieve good precision at low flow rates, a tube with very small diameter (less than 1 mm) is necessary, which may cause additional problems in terms of plugging, clogging etc. Moreover, a CMFC requires relative long residence time in the metallic structure, so that problems and undesired side effects like chemical reactions, corrosion, apprehensive effort for pre-heating or pre-cooling may arise.
Therefore, it is an object of the present invention to provide a dosage system for a static mixer, wherein the mass flow can be controlled avoiding or at least decreasing one of the aforementioned drawbacks.